Honestly my experience is that if a site is broken it probably isn't work using. That being said I can't remember the last time something broke. I mostly do research and reading so maybe it is just my use case
I like it. Pretty damn good for privacy, based on Gecko, supports desktop extensions, and developed by the Divested Computing Group (the same one that created and maintains DivestOS).
I use it as a daily driver, but sometimes it's do slow I want to use chromium (cromite) again. I have a website open, I turn off the screen and immediately turn it back on, and the page takes several seconds to load again. And sometimes, it doesn't even load at all and it's just grey. Same thing happens when I switch to another app from Mull. It's annoying, but the extensions and privacy are still worth it.
It would be perfect except that the fingerprint protection includes forcing the screen refresh rate to the lowest common denominator. Scrolling is unbearable.
They need to report whatever number they want while always using the highest rate instead.
Does Firefox standard fingerprint resistance include the refresh rate? Because I use Firefox over mull on Android because of the drastic difference when scrolling.
I'm pretty sure it's the opposite, although it's understandable that it'd give off that illusion.
You might experience a lower framerate in apps because your battery is overheating, but intentionally invoking it (like Mull does) will make your device require less processing power and thus less likely to overheat.
I've started using Fulguris lately, just random tryout. Its actually decent and has a built in content blocker where you can add lists with the big three main ones already being there. I'm not 100% sure how barebones privacy is on it, but it is open source and from what Exodus says there's no trackers (unless you opt into Google Crash Reporting which is off by default). It does have some extra permissions you might not need, so if you want a near-permissionless browser, it might not bwe the one for you.
It is a really good browser just make sure you install ublock origin. The only big privacy issue is the screen resolution but that's really hard to defend against.
You also might want to try running the eff fingerprinting test. It isn't always a good metric but it does give you a decent idea of how well your browser protects your privacy.